SWODY2
SPC AC 041728
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1228 PM CDT TUE SEP 04 2007
VALID 051200Z - 061200Z
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF NE UT...ERN ID
AND WRN WY...
..ERN ID/WRN WY/NE UT...
LATEST WATER VAPOR IMAGERY SHOWS A WELL-DEVELOPED UPPER-LEVEL TROUGH
CENTERED NEAR THE OREGON COAST. THIS FEATURE IS FORECAST TO DIG SEWD
INTO THE INTERMOUNTAIN WEST LATE TONIGHT AND WEDNESDAY WITH THE
LEADING EDGE OF LARGE-SCALE ASCENT SPREADING EWD ACROSS THE SLIGHT
RISK AREA. THE LIFT AHEAD OF THE TROUGH ALONG WITH SFC HEATING
SHOULD SUPPORT SCATTERED THUNDERSTORM DEVELOPMENT ACROSS THE REGION
WEDNESDAY AFTERNOON.
A 60 KT MID-LEVEL JET ASSOCIATED WITH THE UPPER-LEVEL TROUGH WILL
ROUND THE BASE OF THE UPPER-LEVEL TROUGH MOVING ACROSS NRN UT DURING
THE DAY. THIS WILL CREATE STRONG VERTICAL SHEAR PROFILES FAVORABLE
FOR ORGANIZED SEVERE STORMS WHERE INSTABILITY BECOMES MAXIMIZED
WEDNESDAY AFTERNOON. THE MAIN QUESTION IS WHERE THE INSTABILITY AXIS
WILL SET UP AHEAD OF THE APPROACHING TROUGH. MODEL CONSENSUS PLACES
THE STRONGEST INSTABILITY /SBCAPES 500-1000 J/KG/ FROM SALT LAKE
CITY EXTENDING NWD TO NEAR POCATELLO ID WITH DRIER AIR LOCATED SWWD
ACROSS WCNTRL UT AND COOLER SFC AIR LOCATED ACROSS ERN ID. ALTHOUGH
LOW TO MID-LEVEL MOISTURE SHOWN ON FORECAST SOUNDINGS WILL NOT BE
PARTICULARLY GREAT EVEN ALONG THE INSTABILITY AXIS...THE ENHANCED
LIFT...STRONG SHEAR AND COLD AIR ALOFT SHOULD STILL BE FAVORABLE FOR
LARGE HAIL. STORMS THAT FORM EWD ACROSS WRN WY WILL ALSO HAVE ACCESS
TO VERY STEEP LOW-LEVEL LAPSE RATES WHICH COULD ALSO SUPPORT AN
ISOLATED WIND DAMAGE THREAT.
..SE ND/NRN MN/NE SD...
A SLOW MOVING COLD FRONT IS FORECAST TO BE IN PLACE FROM NRN MN
EXTENDING SWWD INTO SERN ND. THIS BOUNDARY WILL BE THE FOCUS FOR
THUNDERSTORM DEVELOPMENT AS LOW-LEVEL CONVERGENCE INCREASES DURING
THE LATE AFTERNOON AND EARLY EVENING. THE GREATEST THUNDERSTORM
COVERAGE SHOULD EXIST ACROSS NRN MN WITH ISOLATED DEVELOPMENT
POSSIBLE ACROSS SE ND AND NE SD WHERE A CAPPING INVERSION WILL BE IN
PLACE. ALTHOUGH VERTICAL SHEAR PROFILES WILL NOT BE PARTICULARLY
STRONG...MODELS FORECAST ENOUGH INSTABILITY FOR A MARGINAL SEVERE
THREAT WEDNESDAY AFTERNOON. STEEP MID-LEVEL LAPSE RATES SHOWN ON
FORECAST SOUNDINGS MAY BE ENOUGH FOR HAIL AND UNIDIRECTIONAL
LOW-LEVEL FLOW PARALLEL TO THE BOUNDARY MAY SUPPORT STRONG GUSTY
WINDS WITH THE MORE ORGANIZED CELLS.
..CNTRL AND ERN TX/FAR NE LA...
THE LATEST WATER VAPOR IMAGERY SHOWS AN UPPER-LEVEL TROUGH LOCATED
ACROSS WEST TX AND THIS FEATURE IS FORECAST TO MOVE EWD ACROSS CNTRL
TX WEDNESDAY. ASCENT WITH THE TROUGH AND SFC HEATING SHOULD SUPPORT
THE DEVELOPMENT OF NUMEROUS THUNDERSTORMS DURING THE AFTERNOON. AT
THE SFC...A MOISTURE GRADIENT WILL REMAIN IN PLACE FROM DEL RIO TX
EXTENDING NEWD TO NEAR DALLAS WITH SFC DEWPOINTS IN THE LOWER 70S F
SEWD OF THIS LINE. IN ADDITION...A LOW-LEVEL JET IS FORECAST TO BE
LOCATED ACROSS CNTRL AND NE TX AND THIS FEATURE COMBINED WITH
LOW-LEVEL DIRECTIONAL SHEAR SHOWN ON FORECAST SOUNDINGS MAY SUPPORT
A MARGINAL SEVERE THREAT. A FEW MARGINALLY SEVERE WIND GUSTS MAY
OCCUR WHERE INSTABILITY BECOMES MAXIMIZED.
.BROYLES.. 09/04/2007
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